Last week in MySQL Server Development (38)

[henrikingo-oracle]

This weekly newsletter gives you a comprehensive overview of what is going on in the MySQL open development project.
It covers September 14 through September 20, 2026, ending Sunday.

_{mysql/mysql-community & mysql/mysql-server | Sep 14 - Sep 20, 2026 | 20 PRs, 10 issues, and 3 Discussions | 1 of 20 PRs merged}

Executive Summary

1. Dr Chi Zhang, from Tsinghua University and known as @DerZc on github, has entered the proverbial building, submitting a selection of 7 bug fixes. Dr Zhang is known for developing methods for finding and then fixing over 400 bugs in various widely used databases, and is a familiar figure at ISSTA, SIGMOD and OOPSLA conferences, among others.
2. Rollback Prepared Transactions Asynchronously During Binlog Crash Recovery by @SongLibing moved its design to the new Markdown-file in the Pull Request format and is waiting for review of the InnoDB side of things.
3. Optimize binlog handling of large transactions (BOLT) by @wxueting-aws remained in detailed design review, with @SongLibing proposing a path to preserve compatibility with binlog compression.
4. Vector search and indexing support for MySQL was opened by @juliaofferman as an experimental vector-index and ANN-search proof of concept, and @jlopusza-oracle began technical review questions.

Merged

• Improve mysqlsh util.dumpInstance() chunking for composite PRIMARY KEY tables … 2 by @ScottStroz — enhancement, Developer / DBA Experience, Contributor Summit May 2026
  The issue closed after @seemasundara reported that composite-primary-key chunking was incorporated in MySQL 26.7 already.

Implementing / Review

Implementation and review work covered recovery, replication, authentication, compiler compatibility, and Shell tooling.

• [Proposal]: Rollback Prepared Transactions Asynchronously During Binlog Crash Recovery … 100 by @SongLibing — enhancement, Performance & Observability

  • Rollback Prepared Transactions Asynchronously During Binlog Crash Recovery … 711 by @SongLibing — OCA Verified, InnoDB, Tests, Docs, Review Requested, Build Passed, MTR Failed
    @jujose-1 continued recovery-design review after the author updated the design; the InnoDB-specific review remains outstanding.

• Improved Binlog Handling of Large Transactions … 683 by @HugoWenTD\

  • Optimize binlog handling of large transactions (BOLT) … 722 by @wxueting-aws — OCA Verified, Replication, Client, Tests, Docs, Review Requested, Build Passed, MTR Failed
    Review continued on the rename-based large-transaction path;
    @jfg956 raised the need to make BOLT's fallback when binlog compression is enabled explicit or to retain BOLT for those transactions.
    @SongLibing suggested supporting binlog compression and group replication rather than falling back.

• Add partial (subset) matching for REQUIRE SUBJECT … 761 by @EtoNagisa — OCA Required, Tests, Build Passed, MTR Failed
  The patch adds an opt-in partial client-certificate-subject match; a review identified coverage concerns around delimiter-only requirements and escaped non-ASCII subjects.

• optimize timer cycles using rdtime on LoongArch64 … 749 by @huchangqiqi — OCA Required, Build Passed, MTR Failed
  The proposed patch uses the LoongArch64 rdtime instruction to optimize timer-cycle measurement.

Design

• Native VECTOR Store and VECTOR INDEX Support for MySQL … 3 by @ScottStroz — enhancement, AI & Cloud, Contributor Summit May 2026, Contributor Summit Aug 2026 (main vector issue)

  • Vector search and indexing support for MySQL … 759 by @juliaofferman — OCA Verified, InnoDB, Optimizer, Tests, Docs, Review Requested
    The experimental proof of concept adds vector indexing and ANN search for VECTOR columns; @jlopusza-oracle posted preliminary questions ahead of a full code review.

  • [Discussion] Transactional Physical Storage for VECTOR Values in InnoDB … 138 by @zhaiwx1987
    The new design proposes separate InnoDB-managed storage for authoritative VECTOR values, with copy-on-write updates, fixed-slot allocation, and chunked storage for large values.

  • [VI] Vector Index Metadata persistence in the Data Dictionary … 750 by @phulakun
    The proposal specifies storing vector-index type, algorithm, and options in mysql.indexes; no in-period comment was returned to explain the recorded update.

  • [VI] Syntax and functions for using vectors … 751 by @roylyseng
    The specification covers vector functions and optimizer conditions for vector-index scans; the returned comments did not explain the recorded in-period update.

• Feature #684: In-memory Relaylog … 743 by @yangxt-aws — OCA Verified, Replication, Tests, Docs, Review Requested
  @karolina-szczepankiewicz described the design as in good shape while identifying items for discussion; @nacarvalho also reviewed the design, and the author described the code as validation material.

Planning / PoC

• [POC] Prototyping - MySQL User Defined Types … 707 by @marcalff — OCA Verified, InnoDB, Pluggable, Build, Tests, Review Requested, Build Passed, MTR Failed, User Defined Types
  The explicitly non-production UDT prototype received an additional automated review pass during the week.

New

• None.

Bug Fixes

• Bug#102586: multi-table DELETE with ON DELETE CASCADE breaks row-based replication … 719 by @matanbaruch — OCA Verified, Optimizer, Tests, Review Requested, Build Passed, MTR Passed
  The author reported all builds and MTR shards green and requested the remaining Runtime-team review for the dependency traversal.

• Bug#121124 Ignore unchanged CHECK columns for online DDL … 723 by @modasserbillah — OCA Verified, Tests, Review Requested, Build Passed, MTR Passed
  After a rebase and formatting adjustment, checks were green; the discussion recorded that another review was still required before the patch could proceed.

• Fix clang-23 -Wunused-but-set-global errors … 764 by @inikep — OCA Required, InnoDB, Replication, Client, Pluggable, Build Passed, MTR Passed
  The change removes or annotates globals that trigger Clang 23 maintainer-build errors; the author reported a full Clang 23 build with no remaining instances of that warning.

• Fedora RPM Packaging Issues … 137 by @sjmudd — bug
  @jfg956 asked for a title, which @sjmudd added; the report documents missing Fedora build requirements, configuration differences, and MTR resource pressure.

• Bug#121179: Respect empty window frames for const-table rows … 766 by @DerZc — OCA Required, Optimizer, Tests, Build Passed
  The patch corrects window-function results when a const-table row falls outside its frame; a review reported two potential correctness issues in the new RANGE handling.

• Bug#121018: Preserve EXISTS semantics when decorrelating LIMIT … 767 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Failed
  The fix prevents a decorrelated EXISTS or NOT EXISTS subquery from applying LIMIT across all correlation keys; review recommended additional LIMIT and OFFSET coverage.

• Bug#120476: Check key direction before treating a scan as rowid ordered … 768 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Passed
  The patch requires sort-direction compatibility before identifying an index scan as rowid ordered; review found that the regression test did not demonstrate the mismatched ordering case.

• Bug#120475: Separate covered and equality-constrained ROR fields … 769 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Failed
  The change separates equality-constrained fields from merely covered fields when calculating rowid-ordered intersection selectivity.

• Bug#121270: Retain nullable constant fields for DISTINCT aggregation … 770 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Failed
  The patch retains nullable constant-like DISTINCT arguments in temporary tables so NULL rows are not incorrectly counted.

• Bug#121269: Require validated conversion before integer IN comparison … 771 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Failed
  The fix limits integer-comparison conversion to paths where a lossless conversion has been validated, avoiding false matches against non-integral strings.

• Bug#121239: Preserve set-operation state across shared CTE references … 772 by @DerZc — OCA Required, Optimizer, Tests, Build Passed, MTR Failed
  The patch preserves set-operation state and propagates row limits across cloned handles for shared materialized CTEs.

• Fix typos in mysql docs … 763 by @kazanzhy — OCA Required, Build Passed, MTR Failed
  The documentation-only patch corrects three typos; the returned review found no issues in those changes.

Misc / GitHub-platform and process fixes

Repository process activity included contributor onboarding, documentation corrections, and Codex workflow budget reports.

• [aw] Codex PR Review exceeded daily AI credits budget … 765 by @github-actions[bot] — agentic-workflows
  This issue was filed 3 times.